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Why there is an Oblique shock inside the Cd nozzle for the ideal flow condition?

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Old   May 14, 2020, 04:39
Default Why there is an Oblique shock inside the Cd nozzle for the ideal flow condition?
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Using the Area ratio (A/A*) and for the desired exit Mach number I have designed a cd nozzle. The Inlet total pressure (Po) and the total temperature (To) is calculated using Isentropic relations for the optimum condition.

Nozzle divergence angle: 6 degree

Mesh Orthogonal Quality:
Nodes: 51660
Min: 0.9724
Max: 1
Average: 0.997

Solver type: Density-based, Absolute, 2d, Axisymmetric

Model: Energy On, Inviscid

Material: Air (Ideal gas)

Boundary condition:
Inlet- Pressure inlet- 792812.3356 Pa; Supersonic/Initial Gauge pressure: 700000 Pa; Total Temperature: 518.4 K
Outlet- Pressure outlet- 101325 Pa; Backflow total temperature: 288 K
Operating condition- 0 Pa
Wall- Wall

For this condition, I should get an ideal flow throughout the nozzle, but there's an oblique shock inside the cd nozzle. Is this a design flaw or any error in the conditions?
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Old   May 14, 2020, 07:20
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Mach number is not a good indicator of shock. Use static pressure plot to identify the shock. In Mach contours, even shear layers appear as shock.

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ansys, cd nozzle, ideal flow, oblique shock

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